Israeli tanks have moved into Bethlehem in the latest of a series of raids on cities in the West Bank.

A BBC correspondent who watched tanks roll up to within a few hundred metres of the city's Church of the Nativity could hear regular bursts of gunfire.

Rajoub says there are no militants in his compound

Elsewhere in the West Bank, Israeli troops hunting for militants laid siege to the Palestinian security headquarters near Ramallah.

Heavy gunfire was heard from near the compound where the Israeli army says about 50 senior militants wanted for planning suicide bombings and other attacks on Israel are sheltering.

The tanks moved into Bethlehem after Israeli snipers took up position in the nearby Deheisheh refugee camp.

"I can see three tanks on a road just outside Manger Square in the centre of town near the Church of the Nativity, and I've seen soldiers running between the tanks," the BBC's James Reynolds reported from Bethlehem.

"Every few minutes here I've heard the sound of gunfire."

The Israeli army has issued a statement saying it is searching for militants in the city.

Siege

Israeli radio says negotiations are under way at the security compound near Ramallah, which is headquarters to the Palestinian security chief in the West Bank, Jibril Rajoub.

Mr Rajoub himself told Reuters news agency by telephone that the 400 people inside were officials and women employees.

The Israelis have met gunfire from Palestinian fighters

He accused Israel of using helicopter gunships and tanks against the compound and hiding behind human shields, but he added that there would be no surrender.

An Israeli army spokeswoman said Israel wanted to go after militants hiding in the compound but had no intention of harming Mr Rajoub.

The Israeli army says it has made 700 arrests since moving into Ramallah on Friday.

Troops have also been carrying out searches in the town of Qalqilya and tanks have occupied the town of Tulkarm.

Media freeze

Ramallah is now a closed military zone, with troops ensuring Palestinian leader Yasser Arafat's headquarters are off-limits to journalists.

With the city under curfew, residents say they are running out of food.

Israel has been battered by a spate of suicide bombings

Medical supplies are also low in the hospitals and the morgues are full because it is impossible to transport bodies to burial grounds.

Israeli Prime Minister Ariel Sharon says his army's actions are aimed at eliminating once and for all what he calls a terrorist infrastructure.

But his own Foreign Minister, Shimon Peres, has called for "easing the siege" and US President George W Bush has urged Israel to keep open, as he put it, a pathway to peace.

Our correspondent says the media ban prevents Mr Arafat from making defiant statements that make him look more like a hero than a defeated leader.

The Foreign Press Association in Israel has protested strongly against the expulsion of an American television crew from Ramallah.

"Closing an entire city to the media indefinitely is an extreme and unjustified policy that makes it impossible for us to cover the important story unfolding here," it said.

In other developments:

A Katyusha rocket was fired over the Lebanese border into northern Israel but caused no injuries or damage

Israeli troops opened fire on foreign pro-Palestinian demonstrators, wounding at least five foreigners and a Palestinian cameraman - they said they had been provoked by militant supporters.

Palestinian gunmen shot dead 11 suspected collaborators, dragging out bodies to show the media in Tulkarm

An Israeli army sergeant was killed by a sniper in Bethlehem and 16 were wounded elsewhere in the West Bank.